[AW] Disable WebViewLayoutTest.testRequestMIDIAccess due to failures

Disable failing test due to permission model change.
Failing on WebView M and N bots.
(filed crbug.com/929129 to track this issue)

BUG=927055,929129
NOTRY=true
TBR=ntfschr@chromium.org,toyoshim@chromium.org

Change-Id: I9dd4e11036b5a2bc4205da551008423b6ce40350
Reviewed-on: https://chromium-review.googlesource.com/c/1456576Reviewed-by: Tim Volodine <timvolodine@chromium.org>
Commit-Queue: Tim Volodine <timvolodine@chromium.org>
Auto-Submit: Tim Volodine <timvolodine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629578}

android_webview/tools/system_webview_shell/layout_tests/src/org/chromium/webview_shell/test/WebViewLayoutTest.java

@@ -243,6 +243,7 @@ public class WebViewLayoutTest {
         }
     }
 
+    @DisabledTest(message = "crbug.com/929129")
     @Test
     @MediumTest
     public void testRequestMIDIAccess() throws Exception {